Lecture #3: Android Academy Study Jam
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This document summarizes key topics from Udacity Lesson #3 on activities and intents in Android development. It covers listeners, toasts, navigation up vs back, implicit and explicit intents, fragments, shared preferences, and broadcast receivers. For each topic, it provides an overview and sometimes notes potential issues or solutions.
Lecture #3: Android Academy Study Jam
- 1. Lecture #3 Activities && Intents
- 2. General Stuff - Facebook Group - Udacity Lesson #3 - Study Jam Group Signup - My ActionBar looks different - 23/2 No lesson
- 3. Udacity Lesson Overview - Listeners - Toast - UP Navigation vs Back Navigation(TASK) - StartActivity - Intent (bundle) Implicitly & Explicitly - Fragment - Settings - SharedPreferences - BroadCast Receivers
- 4. Toast
- 5. Context - Global information about an application environment - Loading resources, launching a new Activity, obtaining a system service, getting internal file paths, and creating views - Biggest memory leak potential (latter in our sessions)
- 6. Listeners Interface related to view with single callback. Will be called when event is occur
- 7. Event Listeners onClick() - View.OnClickListener onLongClick() - View.OnLongClickListener onFocusChange() - View.OnFocusChangeListener onKey() - View.OnKeyListener onTouch() - View.OnTouchListener onCreateContextMenu() - View guess what :)
- 9. But? - Hard to maintain - Hard to find which button do what - Every class in Java, including anonymous inner classes which create an object and writes accessor methods internally, uses about 500 bytes of code.
- 11. Navigation UP and Back - Task and Backstack - Back navigation is within Task - UP is hierarchical navigation
- 12. Intent - Has address - Has data map: key = value - Has schema You can pass any primitive types and also serializable/Parcelable objects Used to send data/action across the system
- 14. But what if?
- 15. But what if?
- 16. But what if? - Non readable - Mix of static variables - Other activities should know what target expect
- 17. Solution
- 18. Solution
- 19. Fragment The biggest advantage and pain - .commit() asynchronous - any operation after state of Activity was saved - Getting “Context” within Fragment
- 20. Solution - Use callbacks when possible. - Manage internal state of activity and fragment - DialogFragment special treatment
- 21. SharedPreferences - Great thing to store persistent various. - Not accessible by other apps - Used to save things between session and session - Sometimes could be great communication tool (like intent) using “onSharedPreferenceChangeListener”
- 23. But... - Don’t forget that each commit() is IO operation. - use Apply() instead
- 24. Broadcast Receivers Great guy :) - Loose Coupling - 1-to-n relationship - The onReceive() method is always executed on the main thread - You can notify components in your entire application, so the communicating components do not have to "see" each other.
- 25. But... - Marshaling data via intent really hard - Register/Unregister it when you do not needed him (BaseActivity) - Not impossible to transfer large objects